Field of the Invention
The present invention relates to an image forming apparatus.
Discussion of the Background
A conventional image forming apparatus includes a sheet feeder on which a plurality of recording sheets are stacked. The recording sheets stacked on the sheet feeder are drawn out to a conveyance path inside of the apparatus by a sheet feed roller and conveyed to a transfer roller by a plurality of conveyance roller pairs (see Japanese Patent No. 3885869). As typically exemplified by the image forming apparatus disclosed in Japanese Patent No. 3885869, the sheet feeder of the conventional image forming apparatus includes a swingable elevating plate (stacking support). The elevating plate on which recording sheets are stacked is swung vertically by drive means to bring the uppermost recording sheet into contact with the sheet feed roller.
The contents of Japanese Patent No. 3885869 are incorporated herein by reference in their entirety.
In the conventional image forming apparatus, the elevating plate is moved vertically by rotation of gears, and consequently, the speed of the vertical movement is low. Therefore, when the rotation of the sheet feed roller and the vertical movement of the elevating plate are executed by the same drive source, a sheet feed timing by the sheet feed roller varies depending on an amount of recording sheets stacked on the elevating plate (height of recording sheets mounted on the elevating plate). Moreover, in recent years, there has been a demand for reducing an image forming apparatus in size, and there has been proposed an image forming apparatus without conveyance roller pairs between a sheet feed roller and a transfer roller. In the case of such an image forming apparatus having no conveyance roller pairs between the sheet feed roller and the transfer roller, the sheet feed timing may vary depending on an amount of recording sheets stacked on the elevating plate. Then, positions of transfer of toner images to recording sheets differ to hinder acquisition of stable images.
In view of the above-described problems, it is an object of the present invention to provide an image forming apparatus to directly convey a recording sheet from a sheet feed roller to a transfer roller in order to stabilize the conveyance of the recording sheet without increasing the number of component parts.